利用累积挤压制备镁基复合板的塑性调控机制研究

Mg-based composite plates have low density, high specific strength and high specific stiffness, which meet the demand of material to achieve light-weighting in the fields of transportation, aerospace and defense military. At present, few studies have been reported on improving the plasticity of Mg-based composite plates, and their plasticity deformation mechanism has not been fully understood yet. Previous publications indicated that addition of high plasticity component and interface characteristic significantly affected the plasticity of composite, but the mechanism for plastic deformation behavior has not been systematically investigated. In this study, Mg-based composite plates with two different interface characteristics (Mg/Mg and Mg/Al) are fabricated by accumulative extrusion. In order to improve the plasticity of composite plates, a high strength Mg alloy is chosen as the core and Mg alloy or Al alloy with a high plasticity is selected as the sleeve. Via TEM, EBSD and SEM characterization analyses, the effect of the extrusion process and annealing process on the microstructure and plastic deformation behavior is systematically investigated. In this study, the relationship between the plasticity of Mg-based composite plates and the volume fraction of high plasticity components is established and the mechanism of how interface characteristic affects the plasticity is disclosed. In this study, it provides a novel method to fabricate Mg-based composite plates, developing relevant mechanism of tailoring plasticity. This study will provide theoretical support for the application of Mg-based composite plates in the fields of transportation, aerospace and defense military for light-weighting.

镁基复合板具有低密度、高比强度和高比刚度，满足交通运输、航空航天和国防军事领域材料轻量化的需求。目前，在镁基复合板的报道中改善材料塑性方面的研究较少，其塑性变形机制尚不明确。早期文献表明，高塑性组元的引入及界面特征会显著影响复合材料的塑性，但其塑性变形行为机制尚缺乏系统研究。本申请利用累积挤压加工制备Mg/Mg和Mg/Al两种不同界面特征的镁基复合板，通过在高强镁合金表面包覆高塑性镁合金或铝合金层，提升复合板的塑性。拟综合利用TEM、EBSD和SEM等微观结构表征手段，系统研究挤压加工参数和退火工艺对复合板微观组织和塑性变形行为的影响，建立镁基复合板塑性与高塑性组元体积分数之间的定量关系，揭示界面特征影响复合板塑性的机制。通过本项目的研究提出一种新型的制备镁基复合板的加工方法，并发展相应的塑性调控机制，为镁基复合板在交通运输、航空航天和国防军事领域轻量化方面的应用提供理论指导。

本项目利用累积挤压制备不同界面特征的镁基复合板，开展以下几个方面的研究工作：（1）研究挤压工艺和退火制度对镁基复合板微观组织的影响规律；（2）研究挤压态和退火态镁基复合板的力学性能，建立复合板塑性与表层高塑性组元的体积分数之间的定量关系；（3）研究挤压态和退火态的镁基复合板在变形过程中裂纹扩展行为，揭示界面特征影响复合板塑性变形的机制。.本项目的重要进展包括：（1）镁/铝复合板在挤压和退火过程中界面极易形成扩散层，随着退火时间的增加扩散层厚度显著增加，而镁/镁复合板在挤压和退火过程中界面都没有形成明显的扩散层；（2）随着高塑性铝外套体积分数的增加，挤压态的镁/铝复合板的延伸率显著增加。随着退火时间的增加，镁/铝复合板的延伸率大幅降低。随着高塑性镁外套体积分数的增加，挤压态的镁/镁复合板的延伸率显著增加，并且退火后镁/镁复合板的延伸率略有提升；（3）界面特征影响着镁基复合板的断裂行为，进一步显著影响着复合板的塑性变形行为。镁/铝复合材料退火后界面处容易形成大量的脆性金属间化合物，使得复合材料在加载过程中容易开裂，导致界面提前失效，大幅降低镁/铝复合板的整体塑性。.本项目发表SCI论文5篇，申请国家发明专利5件，获批科研项目2项，培养研究生2名。